This invention generally relates to vehicle brake systems. More particularly, this invention is related to a vehicle brake system having a sensor that detects the amount of movement of components within the brake system.
A variety of vehicle braking systems are well known. In some configurations a generally S-shaped cam member serves as an actuator for a drum brake assembly. The cam member acts upon rollers that, in turn, cause movement of brake shoes during a braking application. It is necessary in such braking systems to determine when one or more of the components may need replacement or adjustment.
For example, brake shoe linings wear over time. It is important to monitor the amount of wear on the brake shoe linings to ensure that appropriate maintenance is done in a timely fashion. Additionally, it is useful to determine the total amount of stroke during a braking application. The amount of stroke is typically related to a gap between the brake shoe lining and the inner surface of the drum.
Prior to this invention there has not been a suitable device that has proven to be accurate, robust and economical enough to provide the desired information regarding the components of the brake system. This invention addresses that need and provides a unique arrangement for accurately and efficiently monitoring the operation condition of components within the vehicle brake assembly.
In general terms, this invention is a vehicle brake assembly that includes a sensor that detects the amount of movement of certain components within the brake assembly to indicate certain characteristics of the brake assembly components. A system designed according to this invention includes a drum and a pair of brake shoes each having a lining or engagement surface for selectively engaging an inner surface on the drum during a braking application. A cam member serves as an actuator during a braking application. Rollers preferably are interposed between the brake shoes and the cam member so that the cam member engages the rollers and causes the brake shoe linings to engage the inner surface of the drum during the braking application. A sensor is coupled with the cam member or the rollers and detects the amount of movement of the cam member or rollers during a braking application. The sensor provides a signal that indicates the amount of movement of the cam member or the rollers during a braking application and that information is used to measure characteristics of the components within the brake assembly.
The preferred embodiment includes a rotary sensor that is at least partially supported on the cam member. As the cam member rotates during a braking application, the sensor detects the amount of rotary movement. The amount of rotary movement provides an indication of several characteristics of the brake assembly including the amount of travel of the cam member and brake shoes during a braking application and the thickness of the linings on the brake shoes.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows.